Heat treatment

ABSTRACT

Apparatus for high-speed heat treatment of web stock, particularly coated metallic stock as supplied from a coil, moved in catenary configuration through the heat-treatment apparatus. The apparatus employs a plurality of high-velocity, combustion burner assemblies specially arranged in a plurality of heating zones through which the strip is moved. A plurality of heating sections using these burners usually includes a high-velocity section and a dynamic flow section. Frequently included is a flash-off section to remove volatiles. Special air curtains at the ends of the apparatus serve to close the entry and exit and also remove the cold incoming boundary layer from the stock thereby allowing more efficient operation, and the hot outgoing boundary layer to assure rapid cooling.

iUnited States Patent [1 1 Flynn HEAT TREATMENT {75] Inventor: CharlesS. Flynn, Muskegon, Mich.

[73] Assignee: National Lumbermans Bank & Trust Company, as Trustee forBlu-Surf Thermo Engineering Trust, Muskegon, Mich.

[22] Filed: Nov. 19, 1971 [21] Appl. No.: 200,295

1 1 July to, 1973 Primary Examiner.lohn J. Camby Attorney-Price,Heneveld. Huizenga & Copper [57] ABSTRACT Apparatus for high-speed heattreatment of web stock, particularly coated metallic stock as suppliedfrom a coil, moved in catenary configuration through the heat treatmentapparatus. The apparatus employs a plurality of high-velocity,combustion burner assemblies specially arranged in a plurality ofheating zones through which the strip is moved. A plurality of heatingsections using these burners usually includes a high-velocity sectionand a dynamic flow section. Frequently included is a flash-off sectionto remove volatiles. Special air curtains at the ends of the apparatusserve to close the entry and exit and also remove the cold incomingboundary layer from the stock thereby allowing more efficient operation,and the hot outgoing boundary layer to assure rapid coolingv 14 Claims,4 Drawing Figures Patented July 10, 1973 3 Sheets-Sheet 1 Patented JuiyE0, 1973 3,744,963

3 Sheets-Shoot Patentgd JuEy 10, 1973 3 Sheets-Sheet m m2 0 o a mm o oQMN G v A A HEAT TREATMENT BACKGROUND OF THE INVENTION In recent years,there have been more and more applications where raw materials arepainted or otherwise treated before the finished product is formed.Typical of this is the painting of sheet metal prior to die forming it.To do this, a good coating is required that is durable enough towithstand acids, caustics and, in addition, must be highly abrasive andchip resistant. In many cases, paint containing epoxy-type compounds isused. The advantages of coating the geometrically plain stock ratherthan the geometrically complex final products are obvious. This alsoallows the inside of the product to be completely coated and protected.

Presently, the high cost of these coatings is offset by the ease ofhandling and high speed at which the tinished product can be formed inonly limited areas, however. Due to these high costs, the applicationsutilizing this technique have been limited. The equipment is expensiveand the coatings require temperatures in the range of 250 to 500 F. Thefinish must be completely and evenly distributed and very carefully andclosely controlled. After the coating is applied, the surface cannot betouched until after it has been properly cured as by heat treat-ment. inthe case of coating long strips of stock, as for example, from a roll ofcoiled steel, the length of the treating oven is the crucial factor thatdetermines the speed at which the coating can be applied because it isstrictly controlled by the catenary or sag of the material as it isdrawn through the oven. In presentday equipment, the time that thematerial must be subjected to the heat treatment limits the productionto approximately 100-450 feet per minute. This limiting factor rendersthe process of coating prior to forming economically unfeasible for mostmass production systems, e.g., automobile manufacture. However, by thepresent invention, the heat treatment can acutally be accomplished inless than onethird of the time previously required therefore increasingthe rate of production approximately three times with the resultantcorresponding reduction in costs. Such a drastic improvement hasresulted in the process being economically feasible for mass productionsystem such as automobile manufacture such that at least one of themajor United States automobile manufacturers is now adapting itsmanufacture to this system by using the invention herein.

There are various types of coating that require different treatments.Some that are applied in liquid form require a flashoff time and then abaking process while others can be cured by preheating the metal andthen applying the coating.

The present invention provides an apparatus for heat treatment of webstock such as, for example, sheet metal provided in a large coil. Stockis withdrawn from the coil and coated with a suitable coating materialsuch as paint and then passed through the heat treatment chamber in along continuous catenary web. The heat treatment apparatus of thepresent invention includes a plurality of modular sections arranged intandem along the length of the web as it passes therethrough.

Each of the modular units perform a particular function with respect tothe heat treatment of a particular type of stock. In an applicationrelating to the heat treatment of paint (e.g., epoxy type) applied to aweb of sheet metal, the heat treating apparatus utilizes the followingmodular units arranged in tanden: an exhaust or flash-off section, adynamic-flow oven section, and a high-velocity section. The second andthird sections employ special burners, specially arranged. Air curtainsare provided at both ends, i.e., the inlet and the outlet end, of theapparatus to specially remove boundary layers as well as closing theends, as will be more fully described hereinafter. If desired, a seconddynamic-flow oven and high-velocity section together with an exhaustsection may be provided to further treat the material. Actually, as manymodular units as desired may be provided to treat the material althoughit is normally not necessary because of the extemely high efficiency ofthe invention.

Accordingly, it is a primary object of the present invention to providea high-speed heat treatment apparatus for web stock.

lt is another object of the present invention to provide a heattreatment apparatus utilizing special air curtain jets at the inlet andoutlet ends of the apparatus to remove the boundary layer of air whichfollows the web to enhance the heating, and to remove the boundary layerof hot gases from the web to enhance cooling of the web stock.

It is another object of the present invention to provide a heattreatment apparatus which operates with extremely high efi'iciency andextremely rapidly, thereby rendering coating prior to formingeconomically feasible for many uses, and thus effecting great costsavings as well as enabling superior quality products.

These and other important objects and advantages of this invention willbe readily understood by those skilled in the art upon reading thefollowing specification with reference to the accompanying drawings inwhich:

FIG. 1 is a side elevation view of an apparatus incorporating thepresent invention;

FIG. 2 is an end view of the apparatus shown in HO. 1 illustrating theinlet end;

FIG. 3 is a somewhat schematic elevational crosssectional view takenalong the length of the apparatus in FIG. I; and

FIG. 4 is an enlarged sectional view of one of the burner assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and particularly to FIGS. 1 and 2, a representative heat treatmentapparatus designated by the numeral 10 for the heat treatment of webstock is illustrated. Basically, the apparatus comprises an elongatedtunnel having an inlet end 12 and an exit end 14. lt has a plurality offunctional heat treatment sections including a flash-off section 18, adynamic-flow section 16, and a high velocity section 20. Air curtainmechanisms 22 and 24 are positioned at the inlet end and the outlet endof the tunnel respectively. Each of the sections may be of modularconstruction and conveniently assembled together to form a heattreatment apparatus including some or all of the above-mentionedsections of any desired length and arrangement depending upon theparticular materials being heat treated. When, for example, heattreating paint substances on metallic stock, it is sometimes desirableto have all of the above-named sections, that is,

flash-off, dynamic-flow, and high-velocity, arranged together, with thedynamic flow section being the greatest in length so that a moving webpassing therethrough is subjected to that particular treatment for thegreatest length of time. The flash-off section 18 is provided with ahood 25 at the top thereof and is connected. by conduit means 26 to anexhaust blower 28. Such removes the fumes and volatile substances fromthe stock and passes them through an after burner 30 vented to theatmosphere through an exhaust stack 32.

Referring now additionally to FIG. 3, the various sections of theheat-treatment apparatus will be described in greater detail. Normally,the web W moves along the central portion of the heat-treatmentapparatus in an essentially horizontal plane realizing that it sags incatenary fashion when so supported only at its ends. The varioussections of the apparatus operate above and below the web tosimultaneously treat both surfaces. The upper portion of each sectionwill therefore he described in detail, with like reference numeralsbearing the designation being utilized to designate similar structure inthe lower section.

As the web begins its travel through the apparatus, it first passesthrough the flash-off and exhaust section 18. The flash-off section 18of the apparatus is located adjacent and ahead of the dynamic-flowsection 16 and upstream thereof with respect to the movement of the webW. The flash-off section removes the volatile fumes which can sometimesbe approximately 200 gallons per hour. The fumes are removed by passingthe web through an exhaust plenum where the volatile fumes are removedby an exhaust blower. The removal of the fumes may be accelerated by aplurality of strategically placed air nozzles 52 arranged to direct ajet flow of air toward the surface of the web from above and below. Insome cases, heated air from one of the heating sections may be divertedinto the flash-off section to effectively evaporate the volatilesubstances. In the event the volatiles from the flash-off section are tobe vented to the atmosphere, it is desirable to dissipate the volatilesin a safe manner. An air purifying apparatus including the previouslydescribed exhaust fan 28 and after burner 30 may be provided for thispurpose. The gases are exhausted from the flash-off section at a highrate and passed through the after burner 30 where a plurality of burners54 each similar in construction to burners 44 in the dynamic-flowsection, are located.

The fumes are ignited and burned, and harmless vapors are then passedthrough stack 32 to the atmosphere. A suitable air purifying method andapparatus for treating the volatile substances illustrated in greaterdetail in my US. Pat. No. 3,497,308, issued Feb. 24, 1970, entitled AIRPURIFYING APPARATUS AND METHOD.

The dynamic flow section 16 is a high-efficiency convection heating ovenhaving top walls 33, bottom walls 35, and side walls 37, each of aninsulated construction forming a tunnel-like structure open at its ends.The oven includes a central heated oven chamber 34 and a pair ofoppositely positioned plenum chambers 36 and 36 located adjacent the topand bottom walls of the chamber respectively.

The plenum chambers 36 extend along the length and width of the heaterchamber 34. A plurality of high-volume burner units 38 are arranged toproject hot gases into the oven chamber 34 through a plurality ofelongated, spaced-apart baffle members 40. Air nozzle assemblies 42positioned adjacent the baffles are connected to a source of fluidpressure (not shown) to impart a dynamic Venturi action to the hot gasesinto the oven chamber 34.

The air nozzle assemblies 42 includea series of openings (not shown)drilled into piping 39 which is connected to the source. The openings ororifices are drilled at predetermined intervals along the pipes 39 alongthe width of the oven. The orifices are drilled large enough to supplythe required effective velocity at the work; in other words, the furtherthe jets are from the work, the larger the orifices must be. In onepractical application of the invention, the air is ejected from theorifices at 18,000 ft./min. with a 24 oz. blower as the source. Thiscreates a vacuum that sucks in the heat along the entraining air in thechamber for recirculating and creating a high turbulence that almosteliminates the film coefficient on the material being heated. Theentraining ratio is approximately 40 to 1 minimum; i.e., for every cubicfoot of air ejected from the orifice there are 40 cubic feet minimumsucked intothe stream or entrained, giving the same effect with onecubic foot as normally would exist with 40 CFM flowing at approximately5 5 ft./sec. The higher the temperature that the oven is operating, thegreater the velocity and it follows, the gerater the turbulence.

Each burner assembly 38 includes an elongated manifold 44 supplied witha pressurized combustible mix ture of gases, e.g., natural gas andfiltered air. The air is directed to the manifold 44 from a filter 46through suitable conduit means 48 where it is combined with the gas in amixer 50. A blower assembly 45 is provided to force the air through thefilter and through conduit 48 to the mixer 50. The outlet of the mixeris connected to each of the burner manifolds by conduit means 43.

Referring additionally to FIG. 4, each burner assembly 38 includes aplurality of adjacent, cooperating burner units 39, together extendingsubstantially along the width of the oven within the manifold 44. Theburner units are preferably of the construction shown in my US. Pat. No.3,232,593, issued Feb. 1, 1966, entitled OVEN. Each bumer includes ahollow support housing 41 having an inlet port 43 and an open frontcovered by a thin porous combustion layer 45 sealed to and held over theopen housing front by screen means 47. The combustion layer 45 may be ofa metal fiber, a thin porous ceramic felt, or a fine mesh screen. Thecombustible mixture of gases is forced to pass generally uniformly outof the porous combustion layer to combust at its outer surface. Brackets49 support peripheral upstanding channel'walls 51 forming a hot-gasdirecting elongated outlet passage 53 discharging into the plenumchambers 36 at opposite sides of the web.

Any number of burner assemblies 38 may be arranged in each dynamic-flowsection 16 as required. In the embodiment illustrated in FIG. 1, severaldynamicflow sections-l6 are illustrated, each having an upper and alower burner assembly 38 and 38' respectively, associated therewith. Thedynamic-flow sections are arranged in tandem to form the elongatedheating chamber.

After the web has passed through the flash-off and dynamic-flowsections, it may be subjected to further heat treatment in ahigh-velocity section 20. The highvelocity section includes a pluralityof burners 56 similar to burners 38 and 54 previously described. Theburners 56 are arranged to direct heated gases with high velocity towardthe upper and lower surfaces of the web as it passes through the ovenchamber 57. Each of the high-velocity burners 56 include a number ofindividual burner units having an inlet port, and an open front facecovered by the thin porous combustion layer held in place by a screensuch as that previously described in connection with the dynamic-flowsection and illustrated in FIG. 4. The burners are arranged in amanifold 66 extending across the width of the chamber 57. A plurality ofmanifold burner assemblies $6 are arranged in rows across the chamber,the spacing thereof and the number determined by the particular materialbeing treated. Each high-velocity burner manifold assembly includes apositive pressure chamber 58 similar to the outlet passage 53illustrated in FlG. 4 and has a restricted outlet 60 which produces ahighvolume, high-temperature output of heated gases. The high-velocityoutput is directed toward the web surfaces. The top, bottom, and sidewalls of the burner are constructed of an insulating material 59 similarto that construction shown in connection with the dynamicflow section16. The insulating material and construction for the high-velocitysection must, however, be designed for higher temperatures as thehigh-velocity sections, in continuous operation, tend to reachtemperatures greater than that of the dynamic-flow section.

A combustibe mixture of gases and air is formed in mixer 62 andintroduced through conduit 64 into the manifold chamber 66 of eachburner assembly 56. The volume and temperature output can be regulatedby varying the pressure and the gas mixture input to the burner. Thehigh-volume, high-temperature gases developed on the burner surface areinjected into the pressure chamber 58. Pressure in the chamber 58creates a propelling force to expel the gases through the restrictedoutlet 60 into oven chamber 57. The output flow from the restrictedoutput may be directed in various directions within the oven asillustrated by the arrow shown at outlets 60. In the embodimentillustrated in FIG. 3, the burners 56 located at the inlet end of thehigh-velocity section are directed upstream with respect to movement ofthe web 7 thereby injecting a portion of the high-velocity,high-pressure gases toward the dynamic-flow section 116. For a furtherdetailed discussion of a high-velocity burner unit suitable for use inthe practice of the present invention, reference may be had to my issuedUS. Pat. No. 3,390,944 issued July 2, 1968 entitled HIGH VELOCITY BURNERASSEM- BLY.

The air curtain or boundary layer removal mechanisms 22 and 24positioned at the entrance and exit ends of the heat treatment apparatusare connected by suitable piping 27 to a source of air under pressure.As shown in H05. 2 and 3, the air curtain mechanisms 22 and 24 eachinclude a pair of pipes 23 and 23 extending across the width of the ends12 and 14 of the oven. Each of the pipes have a plurality of orifices ornozzles 29 therein to direct a high-velocity stream of air toward thesurfaces of the web at an acute angle with respect to the opening asindicated by the arrows in FIG. 3. In some applications, the pressureneed only be slightly greater than ambient pressure and the piping means27 may be connected directly to the same pressure source used to supplythe burners.

OPERATION The stock to be subjected to heat treatment is supported ateither end of the heat treatment apparatus in a conventional manner andis drawn through the oven at a predetermined rate depending upon thetreatment desired. After the coating (as, for example, paint) is appliedto the web, the surface cannot be touched until the heat treatment iscompleted. The web stock is painted, coated, or otherwise treated in aconventional manner and enters the heat treatment apparatus at theentrance end (to the left as viewed in FIG. 3). A layer or film of air(sometimes referred to as a boundary layer) follows the surface of theweb as it moves. As the web surface enters the falsh-off section, aircurtain members 2.2 positioned upstream direct a high-velocity stream ofair toward the surface of the web, preferably at an acute angle withrespect thereto, creating a turbulence thereon and remove the clingingboundary layer by peeling it off, thereby exposing the web surface forsubsequent heat treatment. As is well known to those skilled in the art,as the web passes through the flash-off section, the volatile fumes areremoved. This, of course, may be accomplished in any number of ways,although to prevent contamination of the environment, I prefer to treatthe fumes by passing them into after burner 3b as noted previously.Because the exhaust fan 28 creates a reduced pressure area within theexhaust section, an air flows from areas of higher pressure, i.e.,dynamic-flow section 116 and the high-velocity section 20, into theflash-off section. Air jets 52. positioned above and below the web helpto remove the solvents by creating a turbulence and flow of the gaseswhich carry off the volatile solvents. The web then passes into thedynamic-flow section.

The hot gases filling the plenum chamber 36 of the dynamic-flow section16 are driven continuously at a substantial velocity into the ovenchamber 34 by the Venturi action resulting from the high-pressure nozzleassemblies 42. The hot gases and propulsion air mix as they flow intothe oven chamber, thereby providing a relatively high-temperaturedynamic-flow convection heating action on the surfaces of the web in theoven chamber 34.

After paming through the dynamic-flow section, the stock may besubjected to further heat treatment in the high-velocity section 20which provides a more localized application of heated gases. Generally,the highvelocity section provides a heat treatment at a considerablyelevated temperature to cure and set the finishing material. The heatedgases are directed with highvelocity from the restricted outlet sotoward the web surface in the oven chamber 57.

As the web continues its movement out of the highvelocity section, thehot gases create another boundary layer that clings to and follows theweb stock. if the web is drawn out of the oven with the hot gas boundarylayer remaining thereon, the web will tend to stay hot, with the heattending to overcure the finished material. It is therefore desirable toprovide a second air curtain or boundary layer removal means 24 at theoutlet end of the heat treatment apparatus. Jets of air are directedfrom the air curtain mechanism 24 toward the surface of the web,preferably at an acute angle, break up or strip the boundary layer ofheated gases following the web to expose the surfaces of the web to theambient atmosphere to allow rapid cooling thereof. Also, the curtaincloses off the outlet end of the tunnel, and, by being directed with itsacute angle toward the outlet end (see FlG. ll), largely keeps the hotgases inside the oven. As will be obvious to those skilled in the art, a

final exhaust section may be positioned adjacent the outlet end of thehigh-velocity section to carry off heated gases.

The catenary or sag of the web in the oven between its supports at theends thereof determines the length of the web which can be heat treated.This in turn determines the speed at which the coating can be appliedand heat treatment can be accomplished. In prior art systems, the basicfactor involved with all heating operations and which greatly influencesthe retention time in the oven is the heat transfer rate. This in turnis dependent upon oven temperature, the effectiveness of hot gascontact, heat exchange with the article surfaces, radiant heatintensity, and the rate of vapor removal away from the article surfaces.As will become apparent to those skilled in the art, from the foregoingdetailed description, the present invention drastically reduces thenecessary retention time over the conventional equipment by reducing thetime necessary to treat the web. By the present invention, the surfacescan be heat treated in less than one-third of the time necessary forconventional equipment; therefore, production can be increasedapproximately three times over that of the prior art systems, resultingin greatly reduced costs.

While a preferred embodiment of this invention has been illustrated anddescribed, it will be recognized that other embodiments andmodifications of this invention incorporating the teachings hereof maybe readily made in light of this disclosure. All modifications embodyingthe principles of this invention are to be considered as included in theappended claims unless these claims by their language expressly stateotherwise.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.

1. Apparatus for high-speed heat treatment of a coating on a continuousweb comprising:

a first heating chamber;

a second heating chamber positioned downstream of said first heatingchamber, each of said heating chambers having side, bottom, and topwalls forming an elongated tunnel having an inlet end and an exit endfor the web;

exhaust means positioned adjacent said first heating chamber at theinlet end thereof for removing volatile fumes from the coating on theweb;

first hot gas burner means positioned in said first heating chamberadjacent said walls for generating a continuous flow of heated gasesabout the upper and lower surfaces of the web, said hot gas burner meansincluding a plurality of individual burner assemblies, each formed of ahousing having a gas inlet means connected thereto and having meanthereon forming a combustion surface;

second hot gas burner means positioned in said second chamber adjacentsaid walls for directing a high velocity jet of heated gases toward theupper and lower surfaces of the web, said second hot gas burner meansincluding a plurality of individual burner assemblies each havingenclosure means forming a hot-gas pressure chamber, a restricted orificeoutlet from said pressure chamber to allow hot gaseous flow from saidpressure chamber into said second heating chamber while retaining apositive pressure in said pressure chamber, a combustion burner having aburner surface in said enclosure means and gas inlet means connectedthereto, said hot gas pressure pressure chamber and said restrictednozzle outlet causing a high velocity flow of hot combustion gases in ajet stream from said outlet toward the surface of the web;

manifold means connected to said inlet means of each of said first andsaid second hot has burner means to supply a combustible mixturethereto; and

air curtain means positioned at one of said inlet and exit ends toremove the gaseous boundary layer on said web passing through saidchamber.

2. The heat-treatment apparatus as defined in claim 1 wherein saidexhaust means includes a blower, said blower having an inlet and anoutlet to remove the volatile fumes from said exhaust means, said outletconnected to a stack conduit means having a discharge opening therein;burner means in said stack conduit having combustible gas mixture inletmeans thereto and having a hot-gas discharge surface area orientedtoward said discharge end of said stack to create a hotgas flow zonetherein for continuous ignition and combustion of said volatile fumesbefore passage out of said stack.

3. The heat-treatment apparatus as defined in claim 1 wherein saidair-curtain means is positioned at the inlet end of said first heatingchamber er and at the exit end of said second heating chamber to removethe boundary layer of ambient air at the entrance end of said heattreatment apparatus and to remove the boundary layer of heated air atthe exit end thereof.

4. The heat-treatment apparatus as defined in claim 3 wherein saidexhaust means includes a blower, said blower having an inlet and anoutlet to remove the volatile fumes from said exhaust means, said outletconnected to a stack conduit means having a discharge opening therein;burner means in said stack conduit having combustible gas mixture inletmeans thereto and having a hot-gas discharge surface area orientedtoward said discharge end of said stack to create a hotgas flow zonetherein for continuous ignition and combustion of said volatile fumesbefore passage out of said stack.

5. The apparatus as defined in claim 3 wherein said air-curtain means ispositioned at an acute angle with respect to said web and said inlet andexit ends to direct a high-velocity stream of air toward said web topeel the boundary layer from said web.

6. The apparatus as defined in claim 5 wherein said air-curtain means ispositioned adjacent an upper and lower portion of said ends, saidhigh-velocity stream of air is directed toward the upper and lowersurfaces of said web at an angle with respect thereto to peel theboundary layer therefrom and to close said ends to retain the heatedgases in said first and second.

7. The heat-treatment apparatus as defined in claim 5 wherein saidexhaust means further includes a plurality of air nozzles arranged aboveand below said web to direct a continuous jet of pressurized air aboutsaid web to accelerate the removal of volatile fumes therefrom.

8. The heat-treatment apparatus as defined in claim 1 wherein said firstheating chamber includes a plurality of elongated spaced baffle elementsarranged between said hot-gas burners and said web above and below saidweb; pressurized air manifold means adjacent said baffle members toeject pressurized air into said first heating chamber to thereby cause adynamic flow of heated gases in said first chamber about said web.

9. Apparatus for high-speed heat treatment of continuously moving coatedweb stock comprising:

a first heating chamber; a second heating chamber; an exhaust chamberpositioned adjacent said first heating chamber, each of said chambershaving side, bottom and top walls forming an elongated tunnel having aninlet end and an exit end for said web stock; hot-gas burner meanspositioned in each of said chambers adjacent said top and said bottomwalls for directing a continuous flow of heated gases about the upperand lower surfaces of said web;

each of said hot-gas burner means including a plurality of individualburner assemblies, each formed of a housing having a gas inlet meansconnected thereto, an open side covered by a thin porous combustionlayer forming a combustion surface;

manifold means connecting each of said individual burner assemblies to acombustible mixture of gases; and

air-curtain means positioned at said inlet end and said outlet end ofsaid heating chambers to remove the boundary layer from said web passingthrough said chambers and to close said ends.

10. The apparatus as defined in claim 9 wherein said first heatingchamber includes dynamic-flow means cooperating with said burner meansto provide a dynamic flow of heated gases about said web and whereinsaid burners in said second chamber are adapted to direct ahigh-velocity jet of heated gases toward said surfaces.

1 l. The heat-treatment apparatus as defined in claim 9 wherein saidexhaust means includes a blower, said blower having an inlet and anoutlet to remove the volatile fumes from said exhaust means; stackconduit means having a discharge opening therein, said blower meansconnected to said stack conduit means; burner means in said stackconduit having a hot-gas discharge surface thereon oriented toward saiddischarge to create a hot-gas flow zone therein for continuous ignitionand combustion of said volatile fumes before passage out of said stack.

12. The heat-treatment apparatus as defined in claim 11 wherein saidexhaust means further includes a plurality of air nozzles arranged aboveand below said web to direct a continuous jet of pressurized air aboutthe surface of the web to accelerate the removal of volatile fumestherefrom.

13. The apparatus as defined in claim 9 wherein said air-curtain meansis positioned at an acute angle with respect to the web and said inletand outlet ends to direct a high-velocity stream of air toward the webto peel the boundary layer from the web.

14. The apparatus as defined in claim 13 wherein said air-curtain meansis positioned adjacent an upper and lower portion of said ends, saidhigh-velocity stream of air is directed toward the upper and lowersurfaces of the web at an angle with respect thereto to peel theboundary layer therefrom and to close said ends to retain the heatedgases in said first and said second heating chambers.

1. Apparatus for high-speed heat treatment of a coating on a continuousweb comprising: a first heating chamber; a second heating chamberpositioned downstream of said first heating chamber, each of saidheating chambers having side, bottom, and top walls forming an elongatedtunnel having an inlet end and an exit end for the web; exhaust meanspositioned adjacent said first heating chamber at the inlet end thereoffor removing volatile fumes from the coating on the web; first hot gasburner means positioned in said first heating chamber adjacent saidwalls for generating a continuous flow of heated gases about the upperand lower surfaces of the web, said hot gas burner means including aplurality of individual burner assemblies, each formed of a housinghaving a gas inlet means connected thereto and having means thereonforming a combustion surface; second hot gas burner means positioned insaid second chamber adjacent said walls for directing a high velocityjet of heated gases toward the upper and lower surfaces of the web, saidsecond hot gas burner means including a plurality of individual burnerassemblies each having enclosure means forming a hot-gas pressurechamber, a restricted orifice outlet from said pressure chamber to allowhot gaseous flow from said pressure chamber into said second heatingchamber while retaining a positive pressure in said pressure chamber, acombustion burner having a burner surface in said enclosure means andgas inlet means connected thereto, said hot gas pressure pressurechamber and said restricted nozzle outlet causing a high velocity flowof hot combustion gases in a jet stream from said outlet toward thesurface of the web; manifold means connected to said inlet means of eachof said first and said second hot has burner means to supply acombustible mixture thereto; and air curtain means positioned at one ofsaid inlet and exit ends to remove the gaseous boundary layer on saidweb passing through said chamber.
 2. The heat-treatment apparatus asdefined in claim 1 wherein said exhaust means includes a blower, saidblower having an inlet and an outlet to remove the volatile fumes fromsaid exhaust means, said outlet connected to a stack conduit meanshaving a discharge opening therein; burner means in said stack conduithaving combustible gas mixture inlet means thereto and having a hot-gasdischarge surface area oriented toward said discharge end of said stackto create a hot-gas flow zone therein for continuous ignition andcombustion of said volatile fumes before passage out of said stack. 3.The heat-treatment apparatus as defined in claim 1 wherein saidair-curtain means is positioned at the inlet end of said first heatingchamber er and at the exit end of said second heating chamber to removethe boundary layer of ambient air at the entrance end of said heattreatment apparatus and to remove the boundary layer of heated air atthe exit end thereof.
 4. The heat-treatment apparatus as defined inclaim 3 wherein said exhaust means includes a blower, said blower havingan inlet and an outlet to remove the volatile fumes from said exhaustmeans, said outlet connected to a stack conduit means having a dischargeopening therein; burner means in said stack conduit having combustiblegas mixture inlet means thereto and having a hot-gas discharge surfacearea oriented toward said discharge end of said stack to create ahot-gas flow zone therein for continuous ignition and combustion of saidvolatile fumes before passage out of said stack.
 5. The apparatus asdefined in claim 3 wherein said air-curtain means is positioned at anacute angle with respect to said web and said inlet and exit ends todirect a high-velocity stream of air toward said web to peel theboundary layer from said web.
 6. The apparatus as defined in claim 5wherein said air-curtain means is positioned adjacent an upper and lowerportion of said ends, said high-velocity stream of air is directedtoward the upper and lower surfaces of said web at an angle with respectthereto to peel the boundary layer therefrom and to close said ends toretain the heated gases in said first and second.
 7. The heat-treatmentapparatus as defined in claim 5 wherein said exhaust means furtherincludes a plurality of air nozzles arranged above and below said web todirect a continuous jet of pressurized air about said web to acceleratethe removal of volatile fumes therefrom.
 8. The heat-treatment apparatusas defined in claim 1 wherein said first heating chamber includes aplurality of elongated spaced baffle elements arranged between saidhot-gas burners and said web above and below said web; pressurized airmanifold means adjacent said baffle members to eject pressurized airinto said first heating chamber to thereby cause a dynamic flow ofheated gases in said first chamber about said web.
 9. Apparatus forhigh-speed heat treatment of continuously moving coated web stockcomprising: a first heating chamber; a second heating chamber; anexhaust chamber positioned adjacent said first heating chamber, each ofsaid chambers having side, bottom and top walls forming an elongatedtunnel having an inlet end and an exit end for said web stock; hot-gasburner means positioned in each of said chambers adjacent said top andsaid bottom walls for directing a continuous flow of heated gases aboutthe upper and lower surfaces of said web; each of said hot-gas burnermeans including a plurality of individual burner assemblies, each formedof a housing having a gas inlet means connected thereto, an open sidecovered by a thin porous combustion layer forming a combustion surface;manifold means connecting each of said individual burner assemblies to acombustible mixture of gases; and air-curtain means positioned at saidinlet end and said outlet end of said heating chambers to remove theboundary layer from said web passing through said chambers and to closesaid ends.
 10. The apparatus as defined in claim 9 wherein said firstheating chamber includes dynamic-flow means cooperating with said burnermeans to provide a dynamic flow of heated gases about said web andwherein said burners in said second chamber are adapted to direct ahigh-velocity jet of heated gases toward said surfaces.
 11. Theheat-treatment apparatus as defined in claim 9 wherein said exhaustmeans includes a blower, said blower having an inlet and an outlet toremove the volatile fumes from said exhaust means; stack conduit meanshaving a discharge opening therein, said blower means connected to saidstack conduit means; burner means in said stack conduit having a hot-gasdischarge surface thereon oriented toward said discharge to create ahot-gas flow zone therein for continuous ignition and combustion of saidvolatile fumes before passage out of said stack.
 12. The heat-treatmentapparatus as defined in claim 11 wherein said exhaust means furtherincludes a plurality of air nozzles arranged above and below said web todirect a continuous jet of pressurized air about the surface of the webto accelerate the removal of volatile fumes therefrom.
 13. The apparatusas defined in claim 9 wherein said air-curtain means is positioned at anacute angle with respect to the web and said inlet and outlet ends todirect a high-velocity stream of air toward the web to peel the boundarylayer from the web.
 14. The apparatus as defined in claim 13 whereinsaid air-curtain means is positioned adjacent an upper and lower portionof said ends, said high-velocity stream of air is directed toward theupper and lower surfaces of the web at an angle with respect thereto topeel the boundary layer therefrom and to close said ends to retain theheated gases in said first and said second heating chambers.